<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    #app {
        width: 100px;
        height: 100px;
        border: 1px solid #333;
    }
</style>

<body>
    <div id="app" draggable="true">
        可拖拽
    </div>
    <script>
        //单位时间以内只触发一次  如果在这个单位时间之内多次触发，最终只会执行一次
        let timer = null;
        const app = document.getElementById("app");
        app.addEventListener("drag",throttle(function(e){
            console.log(e.offsetY);
        }))
        function throttle(fn,delay=500){
            let timer = null;
            return function(){
                var args = arguments;
                console.log(args);
                if(timer){
                    return
                }
                timer = setTimeout(()=>{
                    console.log(arguments);
                    fn.apply(this.arguments);
                    timer = null;
                },delay)
            }
        }
    </script>
</body>

</html>